The Aqua Lung Argonaut Titanium Blunt Tip knife is one of the best dive knives around. The Argonaut has a straight edge, a serrated edge, blunt tip, and a line cutter. Constructed from tougher than nails titanium, this dive knife will not rust, though rinse it like you normally would. If you find yourself entangled in kelp, seaweed, or monofilament, this is the tool you'll be glad you have. This is your most basic scuba tool, keep it clean, and sharp.